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err总是打开吗？

[英]Are Java System.in/out/err always open?

原文 2018-04-09 04:35:38 5 2 java/ io/ system.out/ system.in/ system.err

Javadoc says in , out and err are 'already open', I just wonder that do they close after program finishes? Javadoc说in ， out和err '已经打开'，我只是想知道它们在程序完成后会关闭吗？ If not does it contradict the practise to close any I/O stream references after use? 如果不是这样，是否与使用后关闭任何I / O流引用的做法相抵触？

2 个解决方案

System.in / out / err these classes are Instantiated by the JVM, not by us. System.in/out/err这些类是由JVM实例化的，而不是由我们实例化的。 Hence JVM will take care of closing them. 因此，JVM将负责关闭它们。

stdin , stdout and stderr are very much a Unix concept, but other operating systems (such as Windows) have copied the concept as well. stdin ， stdout和stderr在很大程度上是Unix概念，但是其他操作系统（例如Windows）也已经复制了该概念。 These are maintained by the system, and you usually don't close them. 这些由系统维护，通常不关闭它们。

However, you can close them, and you even have to close them when you fork() a program, which is the Unix way to have a program detach from the command line and run in the background, such as a daemon. 但是，您可以关闭它们，甚至在使用fork()程序时也必须关闭它们，这是Unix方式，可将程序与命令行分离并在后台运行，例如守护程序。

System.in / out / err follow this strategy. System.in / out / err遵循这一战略。 So you could close them, but you don't have to, because they're special system resources. 因此，您可以关闭它们，但不必这样做，因为它们是特殊的系统资源。